a. Technical Field
The instant disclosure relates generally to mapping of electrical activity within a human body, including the mapping of electrical activity in cardiac tissue.
b. Background Art
Mapping the electrical activity of the heart (i.e., determining the voltage distribution over the heart tissue surface) can be used to examine and diagnose heart activity, such as to detect abnormalities, including arrhythmia. Such electrical activity can be projected onto a map or model of the heart to create, for example, an activation map.
One known way of mapping the electrical activity of the heart is through contact-based mapping, in which one or more electrodes are placed in contact with heart tissue to capture the electrical activity of a particular tissue location. Contact-based procedures, though, can be very time-consuming, as electrical activity at many locations may need to be measured, and the electrode needs to be placed in contact with the tissue at each of those locations. Accordingly, non-contact mapping procedures have been developed.
A non-contact mapping procedure may involve placing a catheter with a large number of electrodes within the heart. One known device for non-contact mapping procedures is the Ensite™ Array™ catheter commercially available from St. Jude Medical, Inc. of St. Paul, Minn. The non-contact mapping catheter may include a basket structure, on which the electrodes are disposed, that may be collapsed for navigation to the interior of the heart and expanded within the heart to perform a mapping procedure. Using a non-contact mapping catheter, electrical activity of the heart may be assessed much more quickly than in a contact-based procedure.
An important element of non-contact mapping is relating voltages on the catheter electrodes to the electrical activity of adjacent heart tissue. This problem, solving for a distribution of voltage over the surface of the heart given a finite set of observed voltages on or in a conducting medium surrounding or within the heart, is colloquially referred to as the inverse problem of electrocardiography. The inverse problem is ill-posed because: (1) the number of observed voltages (i.e., the number of electrodes used to collect measurements) is often less than the number of cardiac surface locations where voltage is to be solved (allowing for non-unique solutions to the problem); and (2) the observed voltages reflect a spatially-averaged version of cardiac surface voltage (making the problem ill-conditioned).